Chemical Fixation of CO2 with Highly Efficient ZnCl/[BMIm]Br Catalyst System

The search for environmentally benign and economic process has been the impetus for much of the research involving epoxide and carbon dioxide coupling in view of the so called "green chemistry" and" atom economy ", since CO2 is a renewable resource and can be used as a safe and cheap C 1 building block to synthesize useful organic compounds without producing any coproducts.[1-2] One of the most attractive synthetic goals starting from carbon dioxide is the chemical fixation of CO2 onto epoxide to afford the five-membered cyclic carbonates (Scheme 1),which are excellent aprotic polar solvents and are used extensively as intermediates in the production of pharmaceuticals and fine chemicals.[3] In the last decades of the twentieth century numerous catalytic systems have been developed for this transformation. While some advances have been obtained, all suffer from either low catalyst stability/reactivity, the need for co-solvent, or the requirement for high pressure and/or catalyst costing expensive.[4] Therefore, to find an effective,not exrensive, environmentally benign and economic catalyst system is urgent.In this paper, chemical fixation of CO2 with mono-substituted terminal epoxides or cyclohexene oxide to form cyclic carbonates under the ZnCl2/[BMIm]Br Catalyst System without using additional organic solvents was achieved in excellent selectivity (＞98%) and TOF(5410h-1) Besides,the pure cis-cyclic carbonate of cyclohexene oxide was obtained in this catalyst system.It was important to note that the catalyst could be recovered by simple vacuum distillation of the corresponding cyclic carbonates and could be used six times almost without losing its catalytic activity and selectivity. The catalyst system was found to be applicable to a variety of terminal epoxides and cyclohexene oxide, forming the corresponding cyclic carbonates in very high TOF and more than 98% selectivity. Based on the obtained results, we also propose the plausible mechanism for this chemical fixation reaction of CO2.     

A novel methodology for the synthesis of cyclic carbonates based on the palladium-catalyzed cascade reaction of 4-methoxycarbonyloxy-2-butyn-1-ols with phenols,involving a novel carbon dioxide elimination-fixation process

A palladium-catalyzed CO(2)-recycling reaction has been developed. Reaction of 4-methoxycarbonyloxy-2-butyn-1-ols with phenols, carried out in the presence of a palladium catalyst, produces phenoxy-substituted cyclic carbonates by way of a pathway involving a CO(2) elimination-fixation. A variety of propargylic alcohols and phenols participate in these reactions which yield cyclic carbonates with high efficiencies. Stereoselective construction of trans-cyclic carbonates is achieved by using nonsymmetric substrates. Highly enantioselective reactions occur when (S)-BINAP is used as a ligand. Reaction of 4-phenoxycarbonyloxy-2-butyn-1-ol in the presence of the palladium catalyst yields the corresponding cyclic carbonates via a three-component decomposition-reconstruction process.     

O-Tosylaminobenzaldehyde aminals in the synthesis of 1,3-disubstituted propargylamines,derivatives of 3H-2-vinylidene-3-aminoindoline and quinoline

o-Tosylaminobenzaldehyde aminals react with propargyl alcohol and its phenyl ether on heating in acetonitrile in the presence of CuI to yield 3H-2-vinylidene-3-aminoindoline derivatives. Analogous reactions with phenylacetylene and dimethylethynylcarbinol result in 1,3-disubstituted propargylamines. The possibility of using the latter compounds in synthesis of quinoline derivatives was shown: cyclization of 1-(o-tosylaminophenyl)-1-morpholino-3-phenylprop-2-yne in the presence of H₂SO₄ and KOH gave 2-phenylquinoline and 2-phenyl-4-morpholinoquinoline, respectively. 3H-2-Phenoxymethylvinylidene-3-morpholinoindoline was studied by X-ray diffraction spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2236–2240, November. 1995.     

Formation of quaternary carbon center with a trifluoromethyl group using a Pd-catalyzed allylation reaction

Synthesis of compounds with quaternary carbons is one of the most attractive reactions in the synthetic chemistry. However, there are only a few reports on synthesis of the compounds with a fluoroalkyl group at a quaternary carbon center. Recently, we reported the synthesis of alpha-trifluoromethylated ketones by the reaction of alpha,beta-unsaturated ketones with CF(3)-I using a Rh catalyst. When the alpha-trifluoromethylated ketones and allyl carbonates were treated with a Pd catalyst, the allylation reaction proceeded smoothly at the trifluoromethylated carbon to give the desired compounds with a trifluoromethylated quaternary carbon center in good to excellent yields.     

Palladium-catalyzed benzylation of active methine compounds without additional base: remarkable effect of 1,5-cyclooctadiene

[reaction: see text] The palladium complex prepared from DPPF and Cp(eta3-C3H5)Pd is an effective catalyst for the alkylation of active methine compounds with benzylic carbonates under neutral conditions. The addition of 1,5-cyclooctadiene brought about remarkable improvement in the lifetime of the palladium catalyst, which led to high yields of the desired benzylation products.     

Experimental and theoretical studies on hydrogen bond-promoted fixation of carbon dioxide and epoxides in cyclic carbonates

The hydrogen bond donor-promoted fixation of CO(2) and epoxides into cyclic carbonates was investigated through experimental and density functional theory studies. A highly effective homogeneous system of 1,2-benzenediol-tetrabutyl ammonium bromide (TBAB) and heterogeneous poly-ionic liquids were developed for the fixation of CO(2) into cyclic carbonates via hydrogen bond activation, based on the understanding of the reaction mechanism and catalyst design. The work hence provides a molecular level understanding of the reaction process and forms the basis for the rational design of catalytic systems for the fixation of CO(2) into useful organic compounds.     

Aminals in the synthesis of 1,3-substituted propargylamines and 3H-2-vinylidene-3-aminobenzofuran derivatives

Aminals of aromatico-hydroxyaldehydes react when heated with terminal acetylenes to form, depending on the reaction conditions and the nature of the starting compounds, 1,3-substituted propargylamines or 3H-2-vinylidene-3-aminobenzofuran derivatives, the structures of which were established by X-ray diffraction.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 455–460, March, 1994.     

Experimental and Computational Studies on Cobalt(I)-Catalyzed Regioselective Allylic Alkylation Reactions

Here, we report the development of cobalt(I)-catalyzed regioselective allylic alkylation reactions of tertiary allyl carbonates with 1,3-dicarbonyl compounds. A family of well-defined tetrahedral cobalt(I) complexes bearing commercially available bidentate bis(phosphine) ligands [(P,P)Co(PPh₃)Cl] are synthesized and explored as catalysts in allylic alkylation reactions. The catalyst [(dppp)Co(PPh₃)Cl] (dppp=1,3-Bis(diphenylphosphino)propane) enables the alkylation of a large variety of tertiary allyl carbonates with high yields and excellent regioselectivity for the branched product. Remarkably, this methodology is selective for the activation of tertiary allyl carbonates even in the presence of secondary allyl carbonates. This contrasts with the selectivity observed in cobalt-catalyzed allylic alkylations enabled by visible light photocatalysis. Mechanistic insights by means of experimental and computational investigations support a Co(I)/Co(III) catalytic cycle.     

Surface modified precipitated calcium carbonates at a high degree of dispersion

Calcium carbonates of different degrees of surface hydrophobicity were obtained when sorbic acid or polyoxyethylene glycol were present during the precipitation. In the presence of trace amounts of divalent cations carbonates with high surface hydrophilicity and improved monodisperse character are obtained. Surface modification of the calcium carbonates by several proadhesive compounds can markedly improve the chemical affinity of the carbonates to polymers. Very effective are isostearoyl titanate and two polyoxyethylene compounds. Precipitated calcium carbonates modified with 2 to 3 percent (wt/wt) of isostearoyl titanate increased the tensile strenght of butadiene-styrene rubber by approximately 100%. Polyurethane is only strengthened when 30 wt/wt of a filler are introduced independently of the type proadhesive compounds. The best strength and hysteresis of polyurethanes are obtained with calcium carbonate modified with 2 percent (wt/wt) of polyoxyethylene glycol.     

Palladium-catalyzed carbon dioxide elimination-fixation reaction of 4-methoxycarbonyloxy-2-buten-1-ols

A new type of palladium-catalyzed CO(2) recycling reaction using allylic carbonates is described. Reaction of trans-4-methoxycarbonyloxy-2-buten-1-ols in the presence of a palladium catalyst produces cyclic carbonates having a vinyl group via a CO(2) elimination-fixation process. A variety of allylic carbonates participate in the reaction giving cyclic carbonates with high efficiencies. Stereoselective construction of trans-cyclic carbonates is achieved by using nonsymmetric substrates. An enantiospecific reaction proceeds to give chiral cyclic carbonate when a chiral methyl-substituted substrate is subjected to the reaction conditions.     

N-heterocyclic carbene catalyzed cyanation reaction of carbonyl compounds with ethyl cyanoformate and acetyl cyanide

N-heterocyclic carbene (NHC) has been employed as an efficient catalyst for cyanation reaction of carbonyl compounds. Under catalysis of 1 mol % NHCs, various aldehydes and 2,2,2-trifluoroacetophenone coupled with ethyl cyanoformate in THF to provide cyanohydrins ethyl carbonates in excellent yields. While in the presence of 10 mol % catalyst, different types of aldehydes and 2,2,2-trifluoroacetophenone reacted with acetyl cyanide in dichloroethane to give acylated cyanohydrins in moderate to high yields.     

修饰金鸡纳碱催化的不对称烯丙基烷基化反应

以修饰金鸡纳碱的手性叔胺为催化剂,Morita-Baylis-Hillman碳酸酯与α-取代的β-酮酸酯经不对称烯丙基烷基化反应,以中等收率及较好的非对映选择性和对映选择性合成了一系列具有连续季碳叔碳手性中心的新型烷基取代β-酮酸酯类化合物,其结构经1H NMR和13C NMR表征。     

Low-molecular-weight model study of peroxide cross-linking of ethylene-propylene-diene rubber using gas chromatography and mass spectrometry II. Addition and combination reactions

The dicumyl-peroxide-initiated addition and combination reactions of mixtures of alkanes (n-octane, n-decane) and alkenes [5,6-dihydrodicyclopentadiene (DCPDH), 5-ethylidene-2-norbornane (ENBH) and 5-vinylidene-2-norbornane (VNBH)] were studied to mimic the peroxide cross-linking reactions of terpolymerised ethylene, propylene and a diene monomer (EPDM). The reaction products of the mixtures were separated by both gas chromatography (GC) and comprehensive two-dimensional gas chromatography (GCxGC). The separated compounds were identified from their mass spectra and their GC and GCxGC elution pattern. Quantification of the various alkyl/alkyl, alkyl/allyl and allyl/allyl combination products shows that allylic-radicals comprise approximately 60% of the substrate radicals formed. The total concentration of the products formed by combination is found to be independent of the concentration and the type of alkene. The total concentration of the products formed by addition to the alkene increases with increasing concentration of alkene. In addition, the total concentration of the formed addition products depends strongly on the type of the alkene used, viz. VNBH>ENBH approximately DCPDH, which is a consequence of differences in steric hindrance of the unsaturation. The peroxide curing efficiency, defined as the number of moles of cross-linked products formed per mol of peroxide, is 173% using 9% (w/w) 5-vinylidene-2-norbornane (VNBH). This indicates that the addition reaction is recurrent. All these findings are consistent with experimental studies on peroxide curing of EPDM rubber. In addition, the present results provide more-detailed structural information, increasing the understanding of the mechanism of peroxide curing of EPDM. The described approach to use low-molecular-weight model compounds followed by GC-mass spectrometry (MS) and GCxGC-MS analysis is proven to be a very powerful tool to study the cross-linking of EPDM.     

Formation of Cyanohydrin Carbonates of Aromatic Aldehydes and Aryl Heteroaryl Ketones

Cyanohydrin derivatives cannot be made by direct addition to diaryl ketones due to the unfavourable equilibrium for the addition process.¹ We required a route to cyanohydrin carbonates of type (1, R¹=heteroaryl, R²=a1kyl), and approached their formation via the aromatic aldehyde analogues (2). Such derivatives (2) have been made using a single aqueous phase method,² and acyl analogues have been made using also a two-phase (water/ether) procedure.³ To obtain the carbonates (2) we have found the former method unreliable and that a satisfactory procedure is to stir an aqueous solution of KCN with the aldehyde and alkyl chloroformate in methylene chloride at 10°C (Table 1). Where necessary yields can be increased by the inclusion of a phase transfer catalyst,⁴ benzyltrimethylammonium chloride. A similar procedure, for addition to (heterocyclic) c=N, has recently been reported⁵ for the formation of certain Reissert compounds.     

Catalyst‐Controlled Switch in Chemo‐ and Diastereoselectivities: Annulations of Morita–Baylis–Hillman Carbonates from Isatins

Regulating both the chemo‐ and diastereoselectivity, divergently, of a reaction is highly attractive but extremely challenging. Presented herein is a catalyst‐controlled switch in the chemo‐ and diastereodivergent annulation reactions of Morita–Baylis–Hillman carbonates, derived from isatins and 2‐alkylidene‐1H‐indene‐1,3(2H)‐diones, in exclusive α‐regioselectivity. α‐Isocupreine efficiently catalyzed [2+1] reactions to access cyclopropane derivatives, and the diastereodivergent [3+2] annulations were accomplished by employing either a chiral phosphine or a DMAP‐type molecule. All reactions exhibited excellent chemoselectivities, and good to remarkable stereoselectivities were furnished, thus leading to a collection of compounds with skeletal and stereogenic diversity. Moreover, DFT computational calculations elucidated the catalyst‐based switch in mechanism.     

Benzyl protection of phenols under neutral conditions: palladium-catalyzed benzylations of phenols.

Benzyl protection of phenols under neutral conditions was achieved by using a Pd(eta3-C3H5)Cp-DPEphos catalyst. The palladium catalyst efficiently converted aryl benzyl carbonates into benzyl-protected phenols through the decarboxylative etherification. Alternatively, the nucleophilic substitution of benzyl methyl carbonates with phenols proceeded in the presence of the catalyst, yielding aryl benzyl ethers.     

SalenAl(OPr)催化CO_2和氧化环己烯共聚反应

从1969年Inoue发现ZnEt2-H2O催化CO2和环氧丙烷共聚以来,CO2共聚催化剂经过了30多年的发展,取得了显著的进步.比较重要的催化体系有Et2Zn-助剂;羧酸锌;双金属;卟啉铝;稀土;高位阻二亚胺和SalenMX等.SalenMX是2000年以来发展起来的新型催化体系,与卟啉铝和二亚胺体系一样,它也具有由金属和N/O等原子的螯合结构和较高的位阻.但与卟啉铝相比,它制备更加容易,共聚反应时间也大大缩短;与二亚胺相比,它在空气中稳定,对水分也不敏感.同时也保留了二亚胺体系催化效率高,产物分子量分布窄的特点.如果能在此基础上加以改进,将会发展成为一种较有前途的二氧化碳共聚工业催化剂.     

A bimetallic catalyst and dual role catalyst: synthesis of N-(alkoxycarbonyl)indoles from 2-(alkynyl)phenylisocyanates

3-allyl-N-(alkoxycarbonyl)indoles are synthesized via the reaction of 2-(alkynyl)phenylisocyanates and allyl carbonates in the presence of Pd(PPh(3))(4) (1 mol %) and CuCl (4 mol %) bimetallic catalyst. It is most probable that Pd(0) acts as a catalyst for the formation of a pi-allylpalladium alkoxide intermediate and Cu(I) behaves as a Lewis acid to activate the isocyanate, and the cyclization step proceeds with a cooperative catalytic activity of Pd and Cu. On the other hand, N-(alkoxycarbonyl)indoles are produced via the reaction of 2-(alkynyl)phenylisocyanates and alcohols under a catalytic amount of Na(2)PdCl(4) (5 mol %) or PtCl(2) (5 mol %). Pd(II) or Pt(II) catalyst exhibits dual roles; it acts as a Lewis acid to accelerate the addition of alcohols to isocyanates and as a typical transition-metal catalyst to activate the alkyne for the subsequent cyclization.     

靛红Morita-Baylis-Hillman碳酸酯与环状N-磺酰亚胺的不对称烯丙基烷基化反应研究

本课题组近年来发展的通过路易斯碱催化靛红Morita-Baylis-Hillman(MBH)碳酸酯的烯丙基烷基化反应是合成光学纯3,3-二取代2-氧化吲哚化合物的一种有效方法. 在此基础上, 本文研究了手性叔胺催化靛红MBH碳酸酯与环状N-磺酰亚胺的不对称烯丙基烷基化反应, 通过亲电反应途径以较高的立体选择性(达86% ee, dr＞95∶5)和高收率(达96%)合成C-3位含季碳手性中心的多官能团氧化吲哚产物. 通过简单的转化可以得到含多个手性中心的2-吲哚酮-3,4'-哌啶环类骨架, 这为进一步合成生理活性物质研究奠定了基础.     

新型Br?nsted酸性离子液体催化二氧化碳与环氧化合物偶联反应

设计合成了一系列由碳链长度可调节的Br?nsted酸中心阳离子及Lewis碱中心阴离子构成的酸性离子液体,,并应用于二氧化碳与环氧化合物的偶联反应合成环碳酸酯。考察了离子液体结构以及温度、压力和催化剂用量等参数的影响。结果表明,具有长碳链的离子液体表现出高催化活性及可重复使用性能。离子液体的酸性影响催化活性。